As various home appliances and communication devices become digitalized and highly advanced, implementation of portable displays is in desperate need. In order to realize a portable display, the materials for producing an electrode for display should not only be transparent and exhibit low resistance, but also have a high flexibility to ensure mechanical stability, and a coefficient of expansion that is similar to that of substrates such that even when a device is overheated or under a high temperature there is no short circuits or significant change in the sheet resistance.
Examples of well known conventional materials that can be used as a transparent conductive material include oxides, carbon nanotube (CNT), graphene, polymer conductors, metal nano wires and the like. Among these materials, indium tin oxide (ITO) is widely used to form a thin film layer in a vacuum method, but indium tin oxide is a ceramic material that shows low resistance against flexing or bending of a substrate and therefore easily cracks and causes deterioration of electrode properties. Not only that, due to the rapid expansion of markets for flat panel displays, mobile devices, and touch panels and the limited reserves of indium which is the main material of indium tin oxide (ITO), the price of indium continues to increase causing a threat to the cost competitiveness of transparent conductive films. Therefore, in order to take a dominant position in the fierce competition of display technologies in the near future, it is important to develop an alternative material that could resolve the problems of ITO electrodes.
In the case of polymer conductors, polyacetylene, polypyrrole, polyphenol, polyaniline, PEDOT:PSS and the like are generally used to produce transparent conductive films. However, most polymer conductors have low solubility, the processes involved are fastidious, and it shows colors since its energy band gap is below 3 eV. Furthermore, when a polymer conductor is coated with a thin film in order to increase its transmissivity, its sheet resistance would increase, which causes a problem in actually being used as a transparent electrode. Furthermore, most polymer conductors lack atmospheric stability, and are therefore easily oxidized in the air, deteriorating the electrical conductivity. Therefore, securing the atmospheric stability is an important element in using polymer conductors.
Much research is being carried out on transparent conductive films using CNT, graphene, or metal nano wire, but these materials have problems that need to be solved in order to be used as low resistance transparent conductive films, and thus have not reached the commercialization level yet.
In order to resolve the aforementioned problems, new studies are being conducted on methods for forming fine intaglio grooves using imprinting methods and then charging a metal of low resistance, and in relation thereto, there is a method for pressing a UV curable resin with a fine mold, imprinting, and then charging an Ag paste to form a transparent conductive film. In this method however, since it is difficult to adjust the thickness of the Ag pattern to control the surface roughness of the pattern film, there are limitations to applying the method to applications where electrodes need to be contacted.
Not only that, since the need for large scale flexible displays is recently increasing, there is an urgent need to develop an electrode material having excellent resistance characteristics, flexibility, adaptability with organic materials, and surface flatness.
Thus, there is a need to develop a method for producing a transparent electrode where fine electrode patterns are formed having excellent surface roughness and that may be easily used in contacts between electrodes.